PROCESS TEMPERATURE TRANSMITTER WITH IMPROVED SENSOR DIAGNOSTICS

• US 20140241399A1
• Filed: 02/25/2013
• Published: 08/28/2014
• Est. Priority Date: 02/25/2013
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Rud, Jason H.
• Granted Patent: US 9,222,844 B2
• Time in Patent Office: Days
• US Class Current: 374/184
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 15/007 Testing
• CPC Class Codes: G01K 7/20 in a specially-adapted circuit, e.g. bridge circuit

Abstract

A process temperature transmitter is operable with at least one temperature sensor having a plurality of leads. The temperature transmitter includes measurement circuitry operably coupleable to the at least one temperature sensor to provide an indication of an electrical parameter of the at least one temperature sensor. A controller is coupled to the measurement circuitry to obtain the indication and provide a process temperature output. A current source applies a test current to the plurality of leads simultaneously. Diagnostic circuitry measures a voltage response on each lead in order to provide a diagnostic indication of the temperature sensor.

Claims

1. A process temperature transmitter operable with at least one temperature sensor having a plurality of leads, the temperature transmitter comprising:

measurement circuitry operably coupleable to the at least one temperature sensor to provide an indication of an electrical parameter of the at least one temperature sensor;

a controller coupled to the measurement circuitry to obtain the indication and provide a process temperature output;

a current source configured to apply a test current to the plurality of leads simultaneously; and

diagnostic circuitry configured to measure a voltage response on each lead and responsively to provide a diagnostic indication of the temperature sensor.

2. The process temperature transmitter of claim 1, wherein the temperature sensor is an RTD.

3. The process temperature transmitter of claim 1, wherein the plurality of leads includes four leads.

4. The process temperature transmitter of claim 1, wherein the diagnostic indication is indicative of an electrical short.

5. The process temperature transmitter of claim 1, wherein the diagnostic indication is indicative of an open lead.

6. The process temperature transmitter of claim 1, wherein the diagnostic indication is indicative of sensor degradation.

7. The process temperature transmitter of claim 1, wherein the diagnostic is indicative of a time constant produced by inherent lead resistance and system capacitance on each lead.

8. The process temperature transmitter of claim 1, wherein the circuitry for applying a test current to the plurality of leads simultaneously is disposed within an analog-to-digital converter application specific integrated circuit (ASIC).

9. The process temperature transmitter of claim 1, wherein the diagnostic indication is based on rise time of the voltage response on each lead.

10. The process temperature transmitter of claim 1, wherein the diagnostic indication is based on fall time of the voltage response on each lead.

11. The process temperature transmitter of claim 10, wherein the diagnostic indication is also based on rise time of the voltage response on each lead.

12. A method of diagnosing at least one temperature sensor connection with a process temperature transmitter, the method comprising:

applying a test current to a plurality of leads of the at least one temperature sensor simultaneously;

detecting a voltage response on each lead of the at least one temperature sensor; and

generating a diagnostic indication relative to the at least one temperature sensor based on the voltage response on each lead.

13. The method of claim 12, wherein the at least one temperature sensor includes a plurality of temperature sensors.

14. The method of claim 13, wherein the plurality of temperature sensors are RTDs.

15. The method of claim 12, wherein the diagnostic indication is indicative of an electrical short.

16. The method of claim 12, wherein the diagnostic indication is indicative of an open lead.

17. The method of claim 12, wherein the diagnostic indication is indicative of sensor degradation.

18. The method of claim 12, wherein the diagnostic is indicative of a time constant produced by inherent lead resistance and system capacitance on each lead.

19. The method of claim 12, wherein the method is performed before each temperature sensor measurement.

20. A process temperature transmitter operable with at least one temperature sensor having a plurality of leads, the temperature transmitting comprising:

means for applying a test current to the plurality of leads of the at least one temperature sensor simultaneously;

means for detecting a voltage response on each lead of the at least one temperature sensor; and

means for generating a diagnostic indication relative to the at least one temperature sensor based on the voltage response on each lead.